The present invention relates in general to pipes, and more particularly, to corrugated metal pipes.
Corrugated metal pipe is used extensively in flood control, drainage and sewer systems because of its economic value strength and durability. The pipe is usually fabricated in 20 foot and 24 foot sections; however sections in other lengths are available. Widely used pipe diameters may range from 6 to 216 inches and typical wall thicknesses are 0.052 inches (18 gauge), 0.064 inches (16 gauge), 0.079 inches (14 gauge), 0.109 inches (12 gauge), 0.138 inches (10 gauge) and 0.168 inches (8 gauge).
Corrugated metal pipe derives most of its inherent strength from the corrugations formed into the metal sheets at the time of fabrication. Helical corrugated pipe is corrugated pipe with helical corrugations, fabricated from corrugated metal sheet, with a continuous helical seam. Corrugated metal sheet is a mill product in sheet or coil form for fabricating helical corrugated pipe products. Corrugations commonly used for metal pipes are circular arcs connected by tangents, and are described by pitch and depth. Pitch is measured at right angles to the corrugations from crest to crest on a same side of a pipe sheet. Depth of a corrugation is measured from a crest of a corrugation to the lowest portion of an adjoining valley, both measured on a same side of a pipe sheet. A corrugation is named using its pitch and depth as “pitch by depth.”
A standard “3×1” corrugation profile features a 3 inch pitch and a 1 inch depth. Seven (7) corrugations are included on each side of the metal sheet. The corrugated metal sheet is formed from a flattened sheet width is about 27 inches (specifically 27¼ inches). The finished (corrugated) sheet width is 21′ (+−½ inch) with a lock seam. A standard “5×1” corrugation profile features a 5 inch pitch and a 1 inch depth. Six (6) corrugations are included on each side of the metal sheet. The corrugated metal sheet is formed from a flattened sheet width is about 34 inches (specifically 33 5/16 inches). The finished (corrugated) sheet width is 30″ (+−½ inch) with a lock seam.
For large pipe diameters (over 48 inches), a 3×1 corrugation profile is the established industry profile. The traditional 5×1 corrugation profile utilizes approximately 13% less material that the 3×1 corrugation profile. However, for engineering purposes, pipes with 3×1 and 5×1 corrugation profiles are considered to have the similar enough structural properties to be equal products. Nonetheless, pipe fabricators must stock both metal sheets with 27 and 34 inch flat sheet widths to accommodate desired the 3×1 and 5×1 corrugation profiles.
Accordingly, there exists a need in the art for an improved corrugated pipe arrangement in comparison to the prior art.